1. Technical Field
The present invention relates to a ball screw used for various industrial machines as well as a seal member and a seal structure applicable to the ball screw.
2. Description of the Related Art
Conventionally, there have been publicly well-known ball screw devices each having a ball screw shaft and a ball nut fitted on an outer periphery of the ball screw shaft, and each including: a lip-type seal member having a lip part elastically contacting a periphery of the ball screw shaft at an end of the ball nut; and a cylindrically-shaped wiper-type seal member having a convex part on an inner periphery thereof, which convex part is fitted in grooves of the ball screw shaft such that the cylindrically-shaped wiper-type seal member is fitted on an outer periphery of the ball screw shaft on an outer side of the lip-type seal member in an axial direction (see Patent Document 1). Such a ball screw device including the lip-type seal member and the wire-type seal member used in a combined manner is configured such that foreign substances in the form of fine particles are prevented from entering between the ball screw shaft and the ball nut.
Meanwhile, there have been publicly well-known seal members each formed into the same in shape as the outer periphery of the ball screw shaft (see Patent Document 2). Such seal members are configured such that thin slide rings each made of synthetic resin are set on the outer periphery of the ball screw shaft, and that outer peripheries of the slide rings are tightened by back-up rings each made of synthetic rubber for the purpose of reduction of sliding resistance when fitting the ball screw shaft in the seal members.